1. Field of the Invention
The present invention relates to a technique for obtaining the three-dimensional coordinate position of an operation object.
2. Description of the Related Art
A device operation according to a gesture recognition technique of detecting a user's hand region using a visible light camera or an infrared camera and operating an operation input component (user interface) in accordance with the motion or position of the region is becoming widespread. In these apparatuses, a hand or a finger is detected in an image input from a camera, and an operation event is detected based on its position or motion. In patent literature 1 (Japanese Patent Laid-Open No. 10-177449), light is emitted at a predetermined or temporally changing timing. The intensity of reflected light is converted into the distance value of an object, thereby implementing a gesture input or pointing operation. In patent literature 2 (Japanese Patent Laid-Open No. 2011-22945), a fingertip is detected from an image input by an infrared camera. A rest of the fingertip is detected, thereby generating input event information.
To recognize a touch operation or a gesture operation by a user's finger, the three-dimensional coordinates of the fingertip are needed to be accurately estimated. Although the position or motion in an image can be captured, it is difficult to accurately obtain the three-dimensional coordinates of the fingertip using one camera. In patent literature 2, the operation is performed by sensing a rest of a fingertip without acquiring its three-dimensional coordinates. In patent literature 1, an object is irradiated with light, and the intensity of reflected light is converted into the distance value of the object. However, a change in reflected light caused by the reflection characteristic or surface orientation of the object is neglected. Actually, the intensity (luminance) of the reflected light changes depending on the direction of the finger with respect to the camera or the light source in practice, making it difficult to accurately acquire the distance. It is therefore difficult to accurately detect an operation event by the direction of a finger.